Jim Eshelman wrote:one of the Middle Pillar rituals would be perfect. So would general invocations such as "Thou who art I," etc. from The Ship.

What is a good source for these?

I can't tell you a single specific source.

In an appendix to 776 1/2 I provided the following list of examples, prefixing it with the statement: "Many of the ways of fulfilling this step are actually small rituals themselves. Others are briefer invocations. Some examples include..."

"The Bornless Ritual" (rewritten as Liber Samekh, often mentioned by Crowley as "The Preliminary Invocation" of The Goetia); see the appendices of MTP

"Opening by Watchtower" (an elaboration of the Open of the Portal Ceremony); see Regardie, Ceremonial Magic

"The Opening of the Pyramid" (a personal variation of the opening of the A.'.A.'. Ritual DCLXXI, based on the Neophyte formula)

The Middle Pillar Ritual

The Supreme Invoking Ritual of the Pentagram (of the Five Elements)

The Ritual of the Star Sapphire (A.'.A.'. Liber XXXVI)

Liber Pleiades (for those who are fortunate enough to have it)

The General Exordium or The Particular Exordium from R.R. et A.C. Book Z-2; see Regardie, The Golden Dawn

Crowley's "Hymn to Pan" (from Equinox III:1, or MTP)

The "Rosicrucian Prayer" from the old Adeptus Minor Initiation and other sources (also the variation thereof, "From Thee," &c., which is known to every initiate of T.'.O.'.T.'.)

The Anthem from the Gnostic Catholic Mass (A.'.A.'. Liber XV)

The First and/or Second Enochian Calls (these are invocations of Spirit; their uses are distinct, and they require a specific understanding of their operation)

These, of course, are only a few examples of the many that could be employed.